Phrenic motor neuron loss in an animal model of early onset hypertonia.

Phrenic motor neuron (PhMN) development in early onset hypertonia is poorly understood. Respiratory disorders are one of the leading causes of morbidity and mortality in individuals with early onset hypertonia, such as cerebral palsy (CP), but they are largely overshadowed by a focus on physical function in this condition. Furthermore, while the brain is the focus of CP research, motor neurons, via the motor unit and neurotransmitter signaling, are the targets in clinical interventions for hypertonia. Furthermore, critical periods of spinal cord and motor unit development also coincide with the timing that the supposed brain injury occurs in CP. Using an animal model of early-onset spasticity (spa mouse [B6.Cg-Glrbspa/J] with a glycine receptor mutation), we hypothesized that removal of effective glycinergic neurotransmitter inputs to PhMNs during development will result in fewer PhMNs and reduced PhMN somal size at maturity. Adult spa (Glrb-/-), and wild-type (Glrb+/+) mice underwent unilateral retrograde labeling of PhMNs via phrenic nerve dip in tetramethylrhodamine. After three days, mice were euthanized, perfused with 4% paraformaldehyde, and the spinal cord excised and processed for confocal imaging. Spa mice had ~30% fewer PhMNs (P = 0.005), disproportionately affecting larger PhMNs. Additionally, a ~22% reduction in PhMN somal surface area (P = 0.019), an 18% increase in primary dendrites (P < 0.0001), and 24% decrease in dendritic surface area (P = 0.014) were observed. Thus, there are fewer larger PhMNs in spa mice. Fewer and smaller PhMNs may contribute to impaired diaphragm neuromotor control and contribute to respiratory morbidity and mortality in conditions of early onset hypertonia.NEW & NOTEWORTHY Phrenic motor neuron (PhMN) development in early-onset hypertonia is poorly understood. Yet, respiratory disorders are a common cause of morbidity and mortality. In spa mice, an animal model of early-onset hypertonia, we found ~30% fewer PhMNs, compared with controls. This PhMN loss disproportionately affected larger PhMNs. Thus, the number and heterogeneity of the PhMN pool are decreased in spa mice, likely contributing to the hypertonia, impaired neuromotor control, and respiratory disorders.

Hypopharyngeal Diverticulum: Toward a Unified Understanding of Its Etiopathogenesis.

The etiopathogenesis of Zenker's diverticulum (ZD) remains uncertain. Increased hypopharyngeal pressure due to a hypertonic upper esophageal sphincter results in herniation proximal to the sphincter producing a pulsion diverticulum. Gastroesophageal reflux, which is known to induce shortening of the injured esophagus, likely plays a prominent role in ZD formation by pulling the cricopharyngeus muscle (CPM) away from the anchored inferior constrictor muscle. This creates a "weak zone" encouraging herniation. A bilobed diverticulum may originate from continuation of the fibrous midline raphe inferiorly to developmentally include part of the CPM. We report using laser endoscopy to divide the inter-diverticular septum followed by transmucosal cricopharyngeus myotomy. Presentation of a rare, bilobed diverticulum emphasizes the importance of the midline prevertebral raphe in anchoring the pharyngeal constrictor muscles with respect to the CPM. This lends support to the hypothesis that the etiopathogenesis of ZD is multifactorial while guiding us to a unified understanding of ZD.

Beyond Ohdo syndrome: A familial missense mutation broadens the MED12 spectrum.

Intellectual disability (ID) is estimated to affect 1-3% of the general population and is a common reason for referrals to pediatric and adult geneticists, as well as neurologists. There are many genetic and non-genetic causes of ID; X-linked forms are identifiable through their characteristic inheritance pattern. Current testing methods have been able to identify over 100 genes on the X chromosome responsible for X-linked intellectual disability (XLID) syndromes. MED12 [MIM *300188] (mediator complex subunit 12) mutations have been linked to numerous XLID syndromes, including Lujan, FG, and Ohdo, and MED12 is included in many XLID panels. MED12 is located at Xq13.1 and its product has roles in transcriptional activation and repression. We describe two affected male siblings and their unaffected mother with a novel missense mutation in MED12, c.4147G>A (p.Ala1383Thr). The siblings share some features of Ohdo syndrome, including feeding difficulties, microcephaly, and speech delay. However, additional attributes such as hypertonia, eosinophilic esophagitis, penile chordee, and particular facial dysmorphisms depart sufficiently from individuals previously described such that they appear to represent a new and expanded phenotype. This case lends credence to the evolving theory that the subtypes of Ohdo, and perhaps other MED12 disorders, reflect a spectrum of characteristics, rather than distinct syndromes. As XLID panel testing and whole exome sequencing (WES) becomes a standard of care for affected males, further MED12 mutations will broaden the phenotype of these intriguing disorders and challenge clinicians to rethink the current diagnostic boundaries.

Trak1 mutation disrupts GABA(A) receptor homeostasis in hypertonic mice.

Hypertonia, which results from motor pathway defects in the central nervous system (CNS), is observed in numerous neurological conditions, including cerebral palsy, stroke, spinal cord injury, stiff-person syndrome, spastic paraplegia, dystonia and Parkinson disease. Mice with mutation in the hypertonic (hyrt) gene exhibit severe hypertonia as their primary symptom. Here we show that hyrt mutant mice have much lower levels of gamma-aminobutyric acid type A (GABA(A)) receptors in their CNS, particularly the lower motor neurons, than do wild-type mice, indicating that the hypertonicity of the mutants is likely to be caused by deficits in GABA-mediated motor neuron inhibition. We cloned the responsible gene, trafficking protein, kinesin binding 1 (Trak1), and showed that its protein product interacts with GABA(A) receptors. Our data implicate Trak1 as a crucial regulator of GABA(A) receptor homeostasis and underscore the importance of hyrt mice as a model for studying the molecular etiology of hypertonia associated with human neurological diseases.

Variants in tropomyosins TPM2 and TPM3 causing muscle hypertonia.

Patients with myopathies caused by pathogenic variants in tropomyosin genes TPM2 and TPM3 usually have muscle hypotonia and weakness, their muscle biopsies often showing fibre size disproportion and nemaline bodies. Here, we describe a series of patients with hypercontractile molecular phenotypes, high muscle tone, and mostly non-specific myopathic biopsy findings without nemaline bodies. Three of the patients had trismus, whilst in one patient, the distal joints of her fingers flexed on extension of the wrists. In one biopsy from a patient with a rare TPM3 pathogenic variant, cores and minicores were observed, an unusual finding in TPM3-caused myopathy. The variants alter conserved contact sites between tropomyosin and actin.

Rapamycin attenuates bladder hypertrophy during long-term outlet obstruction in vivo: tissue, matrix and mechanistic insights.

PURPOSE: Previous molecular studies showed that the mTOR inhibitor rapamycin prevents bladder smooth muscle hypertrophy in vitro. We investigated the effect of rapamycin treatment in vivo on bladder smooth muscle hypertrophy in a rat model of partial bladder outlet obstruction. MATERIALS AND METHODS: A total of 48 female Sprague-Dawley® rats underwent partial bladder outlet obstruction and received daily subcutaneous injections of rapamycin (1 mg/kg) or vehicle commencing 2 weeks postoperatively. A total of 36 rats underwent sham surgery and received rapamycin or vehicle. Rats were sacrificed 3, 6 and 12 weeks after surgery. Before sacrifice, voiding was observed in a metabolic cage for 24 hours. Bladder-to-body weight in gm bladder weight per kg body weight and post-void residual urine were assessed. We evaluated Col1a1, Col3a1, Eln and Mmp7 mRNA expression and histology. Two-factor ANOVA and the post hoc t test were applied. RESULTS: Bladder outlet obstruction caused a significant increase in bladder weight in all obstructed groups. Three weeks postoperatively (1 week of treatment) there was no difference in the bladder-to-body weight ratio in the obstructed group. However, at 6 and 12 weeks (4 and 10 weeks of treatment, respectively) the bladder-to-body weight ratio of rats with obstruction plus rapamycin was significantly lower than that of rats with obstruction plus vehicle. Post-void residual urine volume after 6 and 12 weeks of obstruction was lower in obstructed rats with rapamycin compared to that in obstructed rats with vehicle. Rapamycin decreased the obstruction induced expression of Col1a1, Col3a1, Eln and Mmp7. CONCLUSIONS: Rapamycin prevents mechanically induced hypertrophy in cardiovascular smooth muscle. In vivo mTOR inhibition may attenuate obstruction induced detrusor hypertrophy and help preserve bladder function.

Mechanotransduction pathways in skeletal muscle hypertrophy.

In the last decade, molecular biology has contributed to define some of the cellular events that trigger skeletal muscle hypertrophy. Recent evidence shows that insulin like growth factor 1/phosphatidyl inositol 3-kinase/protein kinase B (IGF-1/PI3K/Akt) signaling is not the main pathway towards load-induced skeletal muscle hypertrophy. During load-induced skeletal muscle hypertrophy process, activation of mTORC1 does not require classical growth factor signaling. One potential mechanism that would activate mTORC1 is increased synthesis of phosphatidic acid (PA). Despite the huge progress in this field, it is still early to affirm which molecular event induces hypertrophy in response to mechanical overload. Until now, it seems that mTORC1 is the key regulator of load-induced skeletal muscle hypertrophy. On the other hand, how mTORC1 is activated by PA is unclear, and therefore these mechanisms have to be determined in the following years. The understanding of these molecular events may result in promising therapies for the treatment of muscle-wasting diseases. For now, the best approach is a good regime of resistance exercise training. The objective of this point-of-view paper is to highlight mechanotransduction events, with focus on the mechanisms of mTORC1 and PA activation, and the role of IGF-1 on hypertrophy process.

Effects of acute perinatal asphyxia in the rat hippocampus.

In the present work, we have used a rat animal model to study the early effects of intrauterine asphyxia occurring no later than 60 min following the cesarean-delivery procedure. Transitory hypertonia accompanied by altered posture was observed in asphyxiated pups, which also showed appreciably increased lactate values in plasma and hippocampal tissues. Despite this, there was no difference in terms of either cell viability or metabolic activities such as oxidation of lactate, glucose, and glycine in the hippocampus of those fetuses submitted to perinatal asphyxia with respect to normoxic animals. Moreover, a significant decrease in glutamate, but not GABA uptake was observed in the hippocampus of asphyctic pups. Since intense ATP signaling especially through P2X(7) purinergic receptors can lead to excitotoxicity, a feature which initiates neurotransmission failure in experimental paradigms relevant to ischemia, here we assessed the expression level of the P2X(7) receptor in the paradigm of perinatal asphyxia. A three-fold increase in P2X(7) protein was transiently observed in hippocampus immediately following asphyxia. Nevertheless, further studies are needed to delineate whether the P2X(7) receptor subtype is involved in the pathogenesis, contributing to ongoing brain injury after intrapartum asphyxia. In that case, new pharmacologic intervention strategies providing neuroprotection during the reperfusion phase of injury might be identified.

Neurobehavior of newborn infants exposed prenatally to methadone and identification of a neurobehavioral profile linked to poorer neurodevelopmental outcomes at age 24 months.

The abuse of prescription opioids and heroin by women of childbearing age over the past decade has resulted in a five-fold increase in the number of infants born opioid-dependent. Daily opioid substitution treatment with methadone is associated with less maternal illicit opioid use and improved antenatal care. However, research on the neurobehavioral effects of daily prenatal exposure to methadone on the infant is limited. Using the NICU Network Neurobehavioral Scale (NNNS), we compared the neurobehavior at birth of 86 infants born to opioid-dependent mothers receiving methadone treatment (MMT) with 103 infants unexposed to methadone. Generalized linear models, adjusted for covariates, showed methadone exposed infants had significantly poorer attention, regulation, and quality of movement. They were also significantly more excitable, more easily aroused, exhibited more non-optimal reflexes, hypertonicity, and total signs of stress abstinence. Maternal MMT was also associated with more indices of neonatal abstinence, including: CNS, visual, genitourinary (GI), and state. Latent profile analysis of the NNNS summary scores revealed four distinct neurobehavioral profiles with infants characterized by the most disturbed neurobehavior at birth having the poorest clinical outcomes at birth, and poorer cognitive and motor development at 24 months of age.

Neonatal hypertonia: I. Classification and structural-functional correlates.

Neonatal hypertonic states can be encountered as expressions of abnormal tone and posture. It would be useful for the neonatal neurointensivist to more precisely describe the various presentations of neonatal hypertonia, taking into consideration a classification scheme adopted for hypertonia in children at older ages. An understanding of the ontogeny of muscle tone and posture during fetal and postnatal preterm time periods with maturation to full-term ages will help conceptualize the developmental structural-functional correlates that subserve the evolving expression of this abnormal clinical sign. In the future, a more accurate description of neonatal hypertonic states should be part of the complete clinical examination to help integrate etiology, timing of injury, and neurologic localization before choosing the appropriate therapeutic intervention.

White matter injury correlates with hypertonia in an animal model of cerebral palsy.

Hypertonia and postural deficits are observed in cerebral palsy and similar abnormalities are observed in postnatal rabbits after antenatal hypoxia-ischemia. To explain why some kits become hypertonic, we hypothesized that white matter injury was responsible for the hypertonia. We compared newborn kits at postnatal day 1 (P1) with and without hypertonia after in vivo global fetal hypoxia-ischemia in pregnant rabbits at 70% gestation. The aim was to examine white matter injury by diffusion tensor magnetic resonance imaging indices, including fractional anisotropy (FA). At P1, FA and area of white matter were significantly lower in corpus callosum, internal capsule, and corona radiata of the hypertonic kits (n=32) than that of controls (n=19) while nonhypertonic kits (n=20) were not different from controls. The decrease in FA correlated with decrease in area only in hypertonia. A threshold of FA combined with area identified only hypertonic kits. A reduction in volume and loss of phosphorylated neurofilaments in corpus callosum and internal capsule were observed on immunostaining. Concomitant hypertonia with ventriculomegaly resulted in a further decrease of FA from P1 to P5 while those without ventriculomegaly had a similar increase of FA as controls. Thus, hypertonia is associated with white matter injury, and a population of hypertonia can be identified by magnetic resonance imaging variables. The white matter injury manifests as a decrease in the number and density of fiber tracts causing the decrease in FA and volume. Furthermore, the dynamic response of FA may be a good indicator of the plasticity and repair of the postnatal developing brain.

Insulin and hypertonicity recruit GLUT4 to the plasma membrane of muscle cells by using N-ethylmaleimide-sensitive factor-dependent SNARE mechanisms but different v-SNAREs: role of TI-VAMP.

Insulin and hypertonicity each increase the content of GLUT4 glucose transporters at the surface of muscle cells. Insulin enhances GLUT4 exocytosis without diminishing its endocytosis. The insulin but not the hypertonicity response is reduced by tetanus neurotoxin, which cleaves vesicle-associated membrane protein (VAMP)2 and VAMP3, and is rescued upon introducing tetanus neurotoxin-resistant VAMP2. Here, we show that hypertonicity enhances GLUT4 recycling, compounding its previously shown ability to reduce GLUT4 endocytosis. To examine whether the canonical soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) mechanism is required for the plasma membrane fusion of the tetanus neurotoxin-insensitive GLUT4 vesicles, L6 myoblasts stably expressing myc-tagged GLUT4 (GLUT4myc) were transiently transfected with dominant negative N-ethylmaleimide-sensitive factor (NSF) (DN-NSF) or small-interfering RNA to tetanus neurotoxin-insensitive VAMP (TI-VAMP siRNA). Both strategies markedly reduced the basal level of surface GLUT4myc and the surface gain of GLUT4myc in response to hypertonicity. The insulin effect was abolished by DN-NSF, but only partly reduced by TI-VAMP siRNA. We propose that insulin and hypertonicity recruit GLUT4myc from partly overlapping, but distinct sources defined by VAMP2 and TI-VAMP, respectively.

Preterm fetal hypoxia-ischemia causes hypertonia and motor deficits in the neonatal rabbit: a model for human cerebral palsy?

Prenatal hypoxia-ischemia to the developing brain has been strongly implicated in the subsequent development of the hypertonic motor deficits of cerebral palsy (CP) in premature and full-term infants who present with neonatal encephalopathy. Despite the enormous impact of CP, there is no animal model that reproduces the hypertonia and motor disturbances of this disorder. We report a rabbit model of in utero placental insufficiency, in which hypertonia is accompanied by marked abnormalities in motor control. Preterm fetuses (67-70% gestation) were subjected to sustained global hypoxia. The dams survived and gave spontaneous birth. At postnatal day 1, the pups that survived were subjected to a battery of neurobehavioral tests developed specifically for these animals, and the tests were videotaped and scored in a masked manner. Newborn pups of hypoxic groups displayed significant impairment in multiple tests of spontaneous locomotion, reflex motor activity, and the coordination of suck and swallow. Increased tone of the limbs at rest and with active flexion and extension were observed in the survivors of the preterm insult. Histopathological studies identified a distinct pattern of acute injury to subcortical motor pathways that involved the basal ganglia and thalamus. Persistent injury to the caudate putamen and thalamus at P1 was significantly correlated with hypertonic motor deficits in the hypoxic group. Antenatal hypoxia-ischemia at preterm gestation results in hypertonia and abnormalities in motor control. These findings provide a unique behavioral model to define mechanisms and sequelae of perinatal brain injury from antenatal hypoxia-ischemia.

Long-term effect of shock wave therapy on upper limb hypertonia in patients affected by stroke.

BACKGROUND AND PURPOSE: Spasticity is a disabling complication of stroke and different noninvasive treatments are used to reduce muscle hypertonia. Shock waves are defined as a sequence of single sonic pulses largely used in the treatment of diseases involving bone and tendon as well as muscular contractures. The effect and duration of extracorporeal shock wave therapy (ESWT) was investigated on muscle hypertonia of the hand and wrist. METHODS: A total of 20 patients affected by stroke associated with severe hypertonia in upper limbs were evaluated. Placebo stimulation was performed 1 week before active stimulation in each patient. Evaluation was performed using the National Institutes of Health and Ashworth scales and video monitoring with a digital goniometer before and immediately after placebo or active stimulation. Motor nerve conduction velocity from abductor digiti minimi were recorded. Patients were monitored at 1, 4, and 12 weeks after active treatment. RESULTS: After active ESWT, patients showed greater improvement in flexor tone of wrist and fingers compared with placebo stimulation. At the 1- and 4-week follow-up visits, a significant decrease of passive muscle tonicity was noted on muscles in all patients receiving active treatment. At 12 weeks after therapy, 10 of the 20 patients showed persistent reduction in muscle tone. There were no adverse events associated with ESWT. CONCLUSIONS: ESWT reduces hypertonia of the wrist and finger muscles for > or =12 weeks after treatment. The possible mechanisms of action of ESWT are discussed.

Patient with spinal muscular atrophy with respiratory distress type 1 presenting initially with hypertonia.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disorder caused by mutations in the IGHMBP2 gene and characterized by life-threatening respiratory distress due to irreversible diaphragmatic paralysis between 6weeks and 6months of age. In this study, we describe a two-month-old boy who presented with hypertonia at first and developed to hypotonia progressively, which was in contrast to the manifestations reported previously. Bone tissue compromise was also observed as one of the unique symptoms. Muscle biopsy indicated mild myogenic changes. He was misdiagnosed until genetic screening to be confirmed as SMARD1. SMARD1 is a clinical heterogeneous disease and this case broadens our perception of its phenotypes.

[Clinical and computerized-tomographic correlations in children with cerebral palsy]. / Klinicheskie i komp'iuterno-tomograficheskie korreliatsii pri detskikh tserebral'nykh paralichakh.

Clinical investigation and computed tomography (CT) were performed in 75 children with the infantile cerebral paralysis (ICP). In 63% pathomorphologic changes were found, their rate dependent on ICP form and severity of the motor deficiency. Most frequent finding was ventricular system dilatation which was asymmetrical in majority of patients. Uniform CT changes--frontal atrophy--were found in patients with atonic-astatic form of ICP.

Neurodevelopmental outcome of neonates with vertically transmitted Chikungunya fever with encephalopathy.

Neurodevelopmental follow-up of neonates with vertically transmitted Chikungunya fever has been infrequently reported. We herein report neurodevelopment follow up of two such babies at 3 year of age.

Novel TSEN54 mutation causing pontocerebellar hypoplasia type 4.

Pontocerebellar hypoplasia exhibits a diverse range of etiologies, including six known autosomal recessive, single gene disorders. We describe a molecularly confirmed case of pontocerebellar hypoplasia type 4, a rare and severe neonatal phenotype with a novel TSEN54 mutation, presenting with polyhydramnios, hypertonia, and early neonatal death. The patient manifested severe hypoplasia of the cerebellum and brainstem. The neuropathologic findings in pontocerebellar hypoplasia type 4 develop late in gestation, and therefore prenatal diagnosis with ultrasonography is of limited use. Establishing a molecular diagnosis in the proband is critical for allowing couples to plan future pregnancies.